The working principle of 3.1 frequency converter

Ac motor synchronous speed expression a:
N = 60 f (1 - s) / p type (1)
Type of n - asynchronous motor speed;
F - asynchronous motor frequency;
S - motor slip;
P - motor pole logarithmic.
By type (1), it is known that speed n and frequency f direct proportion, as long as change frequency f can change the motor

speed, when the frequency f in 0 ~ 50 hz range changes, motor speed adjusting range is very wide. Converter is by changing the

motor power frequency to rotating joints realize speed adjustment, is a kind of ideal high efficiency and high performance speed regulation

means.
Frequency converter is used by changing the frequency of the power to change motor speed, be also usually say of frequency

control of motor speed. Converter is divided into into rectangular, hand over frequency two kinds big. At present into

rectangular variable frequency use more extensive, it consists of contact apparatus, intermediate filtering link, inverter of

three parts. Contact apparatus is the role of constant pressure constant frequency of alternating current (ac) transformation

for adjustable dc, through the voltage type or current mode filter for inverter to rotary union provide dc electrical source. Inverter will

dc power supply into adjustable frequency alternating current (ac). Contact apparatus and inverter are thyristor three phase

bridge circuit. Filter by capacitance reactor composition, for inverter provide stable source voltage or current source.
3.2 converter energy saving way
3.2.1 frequency energy saving:
In order to guarantee the reliability of the production, various production machinery in the design with power driven, bore a

certain margin. Motor cannot be in full load under operation, in addition to achieve power driven requirements outside,

superfluous moment increased active power consumption, cause power waste, the pressure on the high side, can reduce motor speed,

so the constant pressure and saving energy. When the motor speed from N1 N2 to change, the motor shaft power P the relationship

is as follows:
P = CN3; Type (2)
Type: P - host hair
N - the main engine rate of revolution
C - constant
When the motor speed from N1 N2 reduce to, its power from P1 reduce to P2. Power change formula type (3)
Thus reduce motor speed can get cubic level energy saving effect.
If water pump efficiency must, when asked adjust flow down, speed N a fall in the proportion of, the shaft power P established

party relationship decline. Namely water pump motor of electric power and speed approximate established party than relationship.

The team when the required flow Q reduce, adjustable frequency converter output frequency make motor speed n in proportion to

reduce. At this time, the motor power P will be made according to three power relationship greatly lower than damper, valve

energy-saving 40 a 50, so as to fiber optic rotary joint achieve the purpose of saving electricity.
For example: a centrifugal pump motor power for 55 kw, when speed down to 4/5 of the original speed, the power consumption is

28.16 kw, save electricity by 48.8%, when speed down to the original speed l / 2, its power consumption is 6.875 kw, save

electricity by 87.5%.